We have newly designed and synthesized a class of photochemical 1,8-naphthalimide dyes. Photochemical investigation strongly suggests that these dyes function as photoalkylation agents following activation to an intermediate state by visible light (circa 420 nm) excitation. The activated species reacts readily with nucleophilic amino acid residues; e.g., tryptophan, tyrosine, cysteine, and methionine. One such dye, 1,14-bis(N-hexyl-3'-bromo- 1,8'-naphthalimid-4'-yl)-1,4,11,14-tetraazatetradecane-5,10-dione, incorporating two reactive 1,8-naphthalimide groups at each end of an intervening structural bridge has been used to achieve photochemical or photoactivated bonding (welding) of collagenous dura mater sheets to each other. Weld shear strengths of up to 425 gm/cm2 (1.14 X 104 Nt/m2) have been obtained.